In a structure for holding a connector (14) mounted on an electronic circuit board (12) inserted and housed in a case (16), there are provided a resin claw (24) formed on the connector, a hole (26) formed on the electronic circuit board and receiving the claw to be engaged therewith, a pair of rails (20a, 20b) formed on an external wall of the connector to protrude in a direction parallel with a direction in which the connector is inserted in the case, and a second rail (32) formed on an internal wall of the case to protrude in the direction in which the connector is inserted, so as to engage with the rails, thereby enabling the connector to be fixed on the board without the use of screws, while ensuring an excellent resistance against twist or shake applied to the connector when a mating connector is inserted to and removed from the connector mounted on the board.